Abstract
An electron microscope study of the morphologic responses of the rabbit lymph node after skin homografting is described. The results demonstate: (a) the appearance of large, round, ribosome-rich cells—hemocytoblasts— during the first set reaction; (b) a striking proliferation of plasma cells during the second set reaction; (c) the absence of hemocytoblasts in the "6-MP tolerant" animals, and (d) large numbers of two types of unusual cells in the "6-MP resistant" animal. The presence of increased numbers of plasma cells in the second set homograft reaction is in agreement with the findings of circulating antibodies in transplantation immunity and indicates the fundamental unity of the dynamics of the cellular response in various immunological phenomena.
